David Irvine has had a high-profile tenure. Photograph: Alan Porritt/AAP

The head of the Australian Security Intelligence Organisation, David Irvine, will leave his role in September, it was revealed on Wednesday.

Irvine told staff on Wednesday that he would step down as director general of security, after agreeing to stay on for an extra six months past his five-year contract while the attorney general, George Brandis, searches for a suitable replacement, Fairfax reported.

The office of Brandis – who Irvine is answerable to – confirmed to Guardian Australia Irvine would leave in September, but would not comment on any progress in seeking a replacement.

Fairfax reports Brandis is expected to seek a replacement from outside Asio, as was done for Irvine’s appointment and those of the previous three director generals.

Irvine has had a unusually high-profile tenure as head of the secretive intelligence agency, amid embarrassing security breaches at Asio’s still-empty new headquarters, and damaging revelations from the US whistleblower Edward Snowden.

"Certain material that has been released by Snowden that is now in the public realm is of very great concern," he told a Senate estimates hearing in November. "That material is Australian material. It is obviously of very great concern to the Australian government."

Irvine said at the time there was "good collaboration and productive collaboration" between Australian intelligence agencies and agencies from friendly countries and allies around the world.

He revealed Asio had conducted an audit of the information it had shared with allies after the revelations were reported. "It stands to reason that is something we would do," he said but would not comment on the nature or scope of the intelligence material.

"We have a good idea of what information we have shared with other allied and friendly agencies, but I won't go into that."

That case was taken to The Hague, and in December last year Asio conducted a raid on lawyers representing East Timor and the whistleblower spy, seizing casework and cancelling the former operative’s passport.

Irvine was also the Australian ambassador to China and the Australian high commissioner to Papua New Guinea.

An Asio chief with a particular interest in Indonesia, Irvine has written two books centred on the country: a 1996 book about Indonesian shadow puppets called Leather Gods & Wooden Heroes: Java's Classical Wayang as well as a 1990 translation of Bisma: Warrior Priest of the Mahabharata by Satyagraha Hurip.